Dishwasher control system

ABSTRACT

A liquid level responsive switch assembly for a dishwasher or like washing appliance including a movable liquid-displaceable member, within the washing chamber, having a plunger extending through an opening in the chamber bottom and operably connected to a switch located outside the chamber, the switch being adapted for positioning to an upper or lower position by vertical movement of the liquid-displaceable member as the liquid level changes within the chamber, said liquid level responsive switch assembly further including movable lever means extending through a second opening in the chamber bottom, said lever means being adapted to hold said movable liquid-displaceable member in its uppermost position when there exists a positive liquid pressure at the pump outlet of the washing appliance, thereby preventing switch movement as a consequence of a temporary liquid level drop within the washing chamber of the appliance.

United States Patent Cushing May 27, 1975 [54] DISHWASHER CONTROL SYSTEM[75] Inventor: Donald S. Cushing, Louisville. Ky. [57] ABSTRACTAssigneei General Elecil'ic p y1 A liquid level responsive switchassembly for a dish- Louis il ev Ky washer or like washing applianceincluding a movable [22] Filed Apr 4 I974 liquid-displaceable member,within the washing chamher. having a plunger extending through anopening in [21] APPL bio-1457337 the chamber bottom and operablyconnected to a switch located outside the chamber, the switch being [52]U 5 Cl H 134/57 73/306, [37/387 adapted for positioning to an upper orlower position [51] l l H 8'08!) 3/02 by vertical movement of theliquid-displaceable mem- [58] Fieid 307/118. 134/56 D 57 bet as theliquid level changes within the chamber,

137/383]. 68/184, 73/306 said liquid level responsive switch assemblyfurther ineluding movable lever means extending through a sec- 0ndopening in the chamber bottom, said lever means [56] References Citedbei ng adapted to hold said movable llqUlCl- UNITED STATES PATENTSdisplaceable member in its uppermost position when L 7/195' Clark 134/57D there exists a positive liquid pressure at the pump out- 3. 7/1967Slewa" at let of the washing appliance, thereby preventing 3334.651 g137,387 switch movement as a consequence of a temporary 105197! D Xliquid level drop within the washing chamber of the 3:72l:783 3/1973Hancock H 134/56 1) x PP Primary Examiner-Robert L. Bleutge 7 Claims, 3Drawing Figures f 42 it DISHWASHER CONTROL SYSTEM BACKGROUND OF THEINVENTION The prior art suggests several control systems commonlyemployed to coordinate the operation of the pump with respect to theliquid level in the washing chamber of an article washing machine suchas a dishwasher. See, for example, US. Pat. Nos. 2,646,067; 3,464,437;and 3,478,373. The operational cycle of such a machine often begins witha fill step that involves actuation of a solenoid operating a waterinlet valve, that is caused to open and allow a liquid flow into thewash chamber of the machinev Various means are available to control thefill operation, such as timer controls or pressure sensitive switches.The possibility of control failure is inherent so, generally, afail-safe means of preventing washing chamber overflow is employed. Aliquid level responsive switch, such as shown in US. Pat. No. 3,464,437,is the type of dependable fail-safe mechanism often utilized. Such afail-safe mechanism usually comprises a buoyant member or float in thewashing chamber, which includes a linkage arrangement to an electricalswitch outside the chamber, so that when the liquid level in the washingchamber rises to a predetermined level, the float rises and activates aswitch, which, in turn, cuts off the current to the solenoid that holdsthe inlet valve open and allows current to flow to the pump motor.

However, certain problems exist with the abovedescribed assembly whichtend to detract from its efficiency and useful life. One such problem isthat during the washing cycle the liquid level in the washing machinevaries considerably and may from time to time fall to a point low enoughto allow the float to drop and trigger the electrical switch, thusstopping the motor and resetting the inlet valve solenoid, which, inturn, allows more liquid to flow into the washing machine, thus creatingan overfill situation.

Another problem that has been associated with the liquid levelresponsive switch in a washing machine relates to excessive wear in theelectrical switch of the assembly. Such excessive wear results from thefact that circulation and agitation of washing liquid in the lowerportion of the washing chamber tend to impart corresponding agitation orrandom motion and oscillation to the float, which motion is translatedthrough the vertical plunger to the electrical switch. Though the motionmay not be so extreme as to actuate the switch, the constant motion andresulting friction to the parts of the switch tend to materially shortenthe operating life thereof.

The present invention overcomes these prior art problems and provides asimple, inexpensive, readily constructed and easily maintained, liquidlevel responsive switch assembly which prevents the float of theassembly from falling to a level which would stop the pump motor andactuate the till mechanism. It thereby prevents overfilling of thewashing chamber and eliminates random agitation and oscillation of thefloat member of the assembly, thereby increasing the useful life of theswitch component of the assembly.

SUMMARY OF THE INVENTION The invention includes a liquid levelresponsive switch assembly which is useful in preventing the washingmachine from filling at any time when the pump is exerting a positiveliquid pressure at its outlet. Specifically, during the wash and rinsecycles and during the drain cycles, the positive pump pressure actuatesa lever means which holds a float in its uppermost buoyed position tokeep a solenoid control switch closed, thereby preventing washing liquidfrom entering the washing chamber. However, when the pump begins tocavitate at the end of a drain cycle, the positive liquid pressure atthe pump outlet is lost and the float within the washing chamber isallowed to drop, thereby permitting actuation of the fill mechanism.

More specifically, the invention includes a dishwasher of the typehaving a washing chamber, spray means contained within said washingchamber for distributing a washing liquid therein, a pump in flowcommunication with the spray means for delivering the washing liquid tothe spray means, a motor driving the pump, an electrical control circuitfor regulating the motor and providing various cycles of operation ofthe dishwasher, and a switch assembly operatively connected to theelectrical control circuit of the dishwasher, and pressure activatedcontrol means in pressure communication with the outlet of the pumpadapted to operate the switch assembly in response to pressure changesat the outlet of the pump. The switch assembly is advantageously aliquid level responsive switch assembly and the pressure activatedcontrol means is normally adapted to maintain the switch assembly in apreset position as a consequence of a positive liquid pressure beingexerted by the pump at its outlet. Preferably, the switch assemblyincludes a float member within the washing chamber capable of beingbuoyed from a first to a second position in response to a change ofliquid level in the washing chamber and a movable plunger connected tothe float member which projects through an opening in a bottom wall ofthe washing chamber. The switch assembly further includes an electricalswitch positioned outside the washing chamber operated by the plunger inresponse to movement of the float. Also, the pressure activated controlmeans preferably includes support means, such as a lever, as the meansadapted to maintain the float in its second position.

DESCRIPTION OF THE DRAWINGS FIG. I is a side elevational view of adishwasher with the sidewall thereof cut away to illustrate the machinesinternal components.

FIG. 2 is a side elevational view of the liquid level responsive switchassembly of this inventionv FIG. 3 is a schematic diagram of a portionof an electrical circuit for a dishwasher showing an electrical switchin accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a dishwasher havinga cabinet 10 including a front wall 11, a rear wall 12 and opposed sidewalls 13 and 14. Enclosed by these walls is washing chamber 17 whichincludes a bottom wall 16 separating the washing chamber 17 from themotor and pump area 18, which contains the motor-pump unit 19.

In operation of the dishwasher assembly of FIG. I, soiled tableware isplaced on the racks 23 and 24 within the washing chamber 17. A timercontrol means 55 is then set to initiate the wash cycle of the machine.Generally, the wash cycle includes a number of rinse and wash steps thatare sequentially actuated by the timer control which is part of theelectrical control circuit shown in FIG. 3. In practice. the timercontrol 55 will generally first allow current to flow through thecontrol circuit, containing a solenoid S2 controlling the water inletvalve, to permit a flow of water to enter the washing chamber. After thewater in the washing chamber 17 rises to a predetermined level, switch50 moves to its up" position and a motor 190 located in the lowercompartment 18 of the cabinet is actuated to drive the pump 19b whichpumps the water upwardly through a vertically extending conduit 20. Thewater then flows from the conduit 20 into a rotatable hollow spray arm21 having a plurality of spaced-apart orifices 22 therein for directingthe water therefrom in a spray pattern upwardly over the soiledtableware supported in the racks 23 and 24. Generally, one or more ofthe orifices 22 of the spray arm 21 are disposed in such a manner so asto provide a propelling jet stream, thereby causing the spray arm torotate on a central vertical axis to insure uniform washing of thesoiled tableware in the racks 23 and 24. After being sprayed on thesoiled tableware, the water collects on the washing chamber floorportion 16 and is continuously recirculated through the pump to cleansethe soiled tableware.

1n the dishwasher of FIG. 1, a liquid level response switch assembly 29is provided to control the amount of water which enters into washingchamber 17. in the event that the water level would temporarily dropduring the wash or rinse cycle, the result would be an overfilling ofthe chamber 17.

The liquid level responsive switch assembly 29, as shown in FIG. 1, ispositioned at a comparatively high point on the floor 16 of the washchamber 17 to permit a normally high water level in the washing chamber17. The normally high water level during any given step in the washcycle is, however, below the horizontal plane in which the rotatablespray arm 21 operates. Thus, the switch assembly 29 can be located on ahigh point of the floor 16, yet below the plane of operation of therotatable spray arm 21 to operate as a liquid level control means.

The improved liquid level responsive switch assembly 29 is illustratedin detail in FIG. 2. The switch assembly 29 comprises a substantiallylarge float or liquid displaceable member 30 of a generally bulbousshape or umbrelladike configuration which has a centrally downwardiyprojecting stern portion or integral plunger 31. The plunger 31 extendsthrough a stand tube or guiding member 34 that is mounted concentricallywith an opening 160 in the floor 16. As shown in FIG. 2, the lowerportion of the plunger 31 extends through the opening 16a to a pointbelow and outside the washing chamber 17 to engage lever 52 locatedoperably above switch 50. Flexible bellows means 40 surrounds the lowerend of plunger 31 and is held in concentric relationship to opening 160by radially outwardly extending annular flange portion 41 which, inturn, is held in sealed relation to the bottom side of floor 16 byfastening means 48 in conjunction with annular flange 36.

Switch housing 51 is mounted on a convenient wall of housing 10 withlever 52 extending into operative contact with the lower portion ofbellows means 40 which, in turn, is contacted by plunger 3] so thatswitch 50 is controlled by the liquid level in washing chamber 17through the relative movement of float 30. Switch 50 is designed to benormally down" and will act to establish electrical current flow throughthe motor circuit shown in FIG. 3 when permitted to move upwardly. Inthe normal operative position of the switch assembly 29, the weight ofthe float 30 and its integral plunger 31 presses downwardly and istransmitted to lever 52, whereby switch S0 is normally depresseddownwardly in its first or down position, thereby permitting electricityto flow through the fill valve solcnoid. Within the housing 51 of switch50, a biasing means (not shown) is provided to normally urge switch 50upwardly in a direction outwardly from the housing. When the liquidlevel in the lower portion of washing chamber 17 rises during the fillcycle, it causes float 30 to be displaced upwardly and thus lever 52adjacent switch 50 is released to allow the switch to move into itsuppermost or second position. After float 30 has risen and switch 50 isin its uppermost position, motor 19 starts and pressure is built up inconduit 20 downstream of the pump outlet. A pressure tap 26 is connectedin flow communication with the pump outlet and, in turn, in flowcommunication with transducer 27. Thus, there is exerted a positivefluid pressure on transducer 27 when pump 19b is pumping washing liquidvTransducer 27 is attached to floor 16 and includes a downwardly biasedpiston 28 located within a cylinder portion 41. Piston 28 may include anappropriate seal member 44 attached to its upper side to prevent liquidfrom passing therearound and proceeding into washing chamber 17. Piston28 is connected to L- shaped lever 42 which extends through opening 16bin floor 16 and which is slidably held in concentric position withincylinder portion 41 by support means 45. The free end of lever 42 isjuxtapositioned below one edge of float 30 so that when a positiveliquid pressure forces piston 28 upwardly against the biasing force ofspring 43, this free end engages and holds float 30 in its uppermostposition. Such an arrangement, being referred to collectively as apressure activated support means, thereby insures that float 30 will notcause switch 50 to move even if the liquid level in the washing chamber17 should temporarily drop to a level which would normally permit float30 to drop to a level which would cause motor to stop and the fillsolenoid to be reactivated. Thus, during the entire wash cycle, as wellas the rinse and drain cycle, float 30 will be held in its uppermostposition and switch 50 will allow cur rent to flow to motor 19. Only atthe end of the drain cycle, when the pump begins to cavitate from a lackof water, will the pressure in the pressure tap 26 drop, thus allowingpiston 28 to drop and, consequently, float 30 to drop, shutting offmotor 19 and reactivating the fill solenoid.

Having thus described the invention, what is claimed 1. In a dishwasherof the type having a washing chamber, spray means contained within saidwashing chamber for distributing washing liquid therein, a pump in flowcommunication with said spray means for delivering said washing liquidto said spray means, a motor driving said pump and an electrical controlcircuit for regulating said motor and providing various cycles ofoperation of said dishwasher, the invention comprising: (a) a switchassembly operatively connected to the electrical control circuit of thedishwasher; and (1)) pressure activated control means in pressurecommunication with the outlet of said pump adapted to operate saidswitch assembly in response to pressure changes at the outlet of saidpump.

2. The combination set forth in claim 1 wherein said switch assembly isa liquid level responsive switch assembly and said pressure activatedcontrol means is adapted to maintain said switch assembly in a presetposition as a consequence of a positive liquid pressure being exerted bysaid pump at its outlet.

3. The combination set forth in claim 2 wherein said switch assemblyincludes a float member within said washing chamber capable of beingbuoyed from a first to a second position in response to a change ofliquid level in said washing chamber, and a movable plunger connected tosaid float member and projecting through an opening in a bottom wall ofsaid washing chamber, and an electrical switch positioned outside saidwashing chamber operated by said plunger in response to movement of saidfloat, and said pressure activated control means includes support meansadapted to maintain said float in its second position.

4. The combination set forth in claim 3 wherein said dishwasher furtherincludes a substantially vertical stand tube having a longitudinalpassage therethrough for operably receiving said plunger therein. andbellows means in combination therewith acting normally to contain saidplunger in its position relative said wash chamber.

5. The combination set forth in claim 3 wherein said pressure activatedcontrol means comprises a pressure tap connected in flow communicationwith said pump outlet and in flow communication with a transducer. saidtransducer being operably attached to L-shaped lever meansjuxtapositioned below one edge of said float to maintain said float inits second position as a consequence of pressure liquid pressure beingexerted by said pump at its outlet.

6. The combination set forth in claim 5 wherein said transducercomprises a downwardly biased piston located within a cylinder portion,said piston having said L-shaped lever attached thereto in slidablerelationship to said cylinder and supported therefrom to allow movementof said piston and said lever as a unit within said cylinder.

7. The combination set forth in claim 6 wherein said piston furtherincludes a seal member attached to its upper side to prevent liquid frompassing between said cylinder and said piston.

1. In a dishwasher of the type having a washing chamber, spray meanscontained within said washing chamber for distributing washing liquidtherein, a pump in flow communication with said spray means fordelivering said washing liquid to said spray means, a motor driving saidpump and an electrical control circuit for regulating said motor andproviding various cycles of operation of said dishwasher, the inventioncomprising: (a) a switch assembly operatively connected to theelectrical control circuit of the dishwasher; and (b) pressure activatedcontrol means in pressure communication with the outlet of said pumpadapted to operate said switch assembly in response to pressure changesat the outlet of said pump.
 2. The combination set forth in claim 1wherein said switch assembly is a liquid level responsive switchassembly and said pressure activated control means is adapted tomaintain said switch assembly in a preset position as a consequence of apositive liquid pressure being exerted by said pump at its outlet. 3.The combination set forth in claim 2 wherein said switch assemblyincludes a float member within said washing chamber capable of beingbuoyed from a first to a second position in response to a change ofliquid level in said washing chamber, and a movable plunger connected tosaid float member and projecting through an opening in a bottom wall ofsaid washing chamber, and an electrical switch positioned outside saidwashing chamber operated by said plunger in response to movement of saidfloat, and said pressure activated control means includes support meansadapted to maintain said float in its second position.
 4. Thecombination set forth in claim 3 wherein said dishwasher furtherincludes a substantially vertical stand tube having a longitudinalpassage therethrough for operably receiving said plunger therein, andbellows means in combination therewith acting normally to contain saidplunger in its position relative said wash chamber.
 5. The combinationset forth in claim 3 wherein said pressure activated control meanscomprises a pressure tap connected in flow communication with said pumpoutlet and in flow communication with a transducer, said transducerbeing operably attached to L-shaped lever means juxtapositioned belowone edge of said float to maintain said float in its second position asa consequence of pressure liquid pressure being exerted by said pump atits outlet.
 6. The combination set forth in claim 5 wherein saidtransducer comprises a downwardly biased piston located within acylinder portion, said piston having said L-shaped lever attachedthereto in slidable relationship to said cylinder and supportedtherefrom to allow movement of said piston and said lever as a unitwithin said cylinder.
 7. The combination set forth in claim 6 whereinsaid piston further includes a seal member attached to its upper side toprevent liquid from passing between said cylinder and said piston.